ARRL Propagation Bulletin ARLP010 (2003)

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SB PROP @ ARL $ARLP010
ARLP010 Propagation de K7VVV
ZCZC AP10
QST de W1AW =20
Propagation Forecast Bulletin 10 ARLP010
From Tad Cook, K7VVV
Seattle, WA March 7, 2003
To all radio amateurs=20
SB PROP ARL ARLP010
ARLP010 Propagation de K7VVV
Thanks to Carl Luetzelschwab, K9LA for filling in and writing last
week's Propagation bulletin.
Carl mentioned the decline of the current solar cycle. During the
early years of the decline (which is where we are now) we see quite
a variation in the solar flux and sunspot numbers from week to week,
although the trend is definitely downward. At the bottom of the
cycle there is very little variation. Just week after week of hardly
any sunspots or none at all.
Check this Propagation bulletin from July 1996 at
http://www.arrl.org/w1aw/prop/1996-arlp031.html. "No sunspots
visible for 11 days in a row," back in the very quiet summer of '96.
This week we saw the average daily sunspot number increase nearly 50
points over the previous week, and average daily solar flux up 30
points. The geomagnetic indices were active after a robust solar
wind arrived on March 3. The most active period was late on March 3
into March 4 when the planetary K index reached 4 and Alaska's
College K index reached 6.
Currently on Thursday evening we are affected by a high-speed solar
wind stream from a coronal hole causing minor geomagnetic storms in
high latitudes. This would result in absorption of HF signals over
polar paths. Geomagnetic indices are expected to be unsettled to
active over the next few days, and solar flux should decline again.
Solar flux is expected to go below 145 by March 10 and then reach a
short-term minimum below 110 around March 22-23.
Since February is over, now we can look at monthly average sunspot
and solar flux numbers to spot a trend. Average daily sunspot
numbers for September 2002 through February 2003 were 206.4, 153.9,
159.8, 144.8, 150.0 and 87.9. Average daily solar flux for those
same months was 175.8, 167.0, 168.7, 157.2, 144.0 and 124.5. This is
quite a decline. The average sunspot number for February of last
year was nearly 107 points higher at 194.5, and average solar flux
was 205, more than 80 points higher than February 2003.
For more information about propagation and an explanation of the
numbers used in this bulletin, see the Propagation page on the ARRL
Web site at, http://www.arrl.org/tis/info/propagation.html and
especially the article "The Sun, the Earth, the Ionosphere," by Carl
Luetzelschwab, K9LA.
Sunspot numbers for February 27 through March 5 were 82, 77, 73, 67,
136, 160, and 138, with a mean of 104.7. 10.7 cm flux was 117.6,
124.9, 138.1, 147.3, 149.1, 146, and 148.5, with a mean of 138.8.
Estimated planetary A indices were 22, 17, 14, 14, 15, 26, and 16,
with a mean of 17.7.
NNNN
/EX
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<P><FONT SIZE=3D2>SB PROP @ ARL $ARLP010</FONT>
<BR><FONT SIZE=3D2>ARLP010 Propagation de K7VVV</FONT>
</P>
<P><FONT SIZE=3D2>ZCZC AP10</FONT>
<BR><FONT SIZE=3D2>QST de W1AW&nbsp; </FONT>
<BR><FONT SIZE=3D2>Propagation Forecast Bulletin 10&nbsp; ARLP010</FONT>
<BR><FONT SIZE=3D2>From Tad Cook, K7VVV</FONT>
<BR><FONT SIZE=3D2>Seattle, WA&nbsp; March 7, 2003</FONT>
<BR><FONT SIZE=3D2>To all radio amateurs </FONT>
</P>
<P><FONT SIZE=3D2>SB PROP ARL ARLP010</FONT>
<BR><FONT SIZE=3D2>ARLP010 Propagation de K7VVV</FONT>
</P>
<P><FONT SIZE=3D2>Thanks to Carl Luetzelschwab, K9LA for filling in and =
writing last</FONT>
<BR><FONT SIZE=3D2>week's Propagation bulletin.</FONT>
</P>
<P><FONT SIZE=3D2>Carl mentioned the decline of the current solar cycle. =
During the</FONT>
<BR><FONT SIZE=3D2>early years of the decline (which is where we are =
now) we see quite</FONT>
<BR><FONT SIZE=3D2>a variation in the solar flux and sunspot numbers =
from week to week,</FONT>
<BR><FONT SIZE=3D2>although the trend is definitely downward. At the =
bottom of the</FONT>
<BR><FONT SIZE=3D2>cycle there is very little variation. Just week after =
week of hardly</FONT>
<BR><FONT SIZE=3D2>any sunspots or none at all.</FONT>
</P>
<P><FONT SIZE=3D2>Check this Propagation bulletin from July 1996 =
at</FONT>
<BR><FONT SIZE=3D2><A =
HREF=3D"http://www.arrl.org/w1aw/prop/1996-arlp031.html">http://www.arrl.=
org/w1aw/prop/1996-arlp031.html</A>. &quot;No sunspots</FONT>
<BR><FONT SIZE=3D2>visible for 11 days in a row,&quot; back in the very =
quiet summer of '96.</FONT>
</P>
<P><FONT SIZE=3D2>This week we saw the average daily sunspot number =
increase nearly 50</FONT>
<BR><FONT SIZE=3D2>points over the previous week, and average daily =
solar flux up 30</FONT>
<BR><FONT SIZE=3D2>points. The geomagnetic indices were active after a =
robust solar</FONT>
<BR><FONT SIZE=3D2>wind arrived on March 3. The most active period was =
late on March 3</FONT>
<BR><FONT SIZE=3D2>into March 4 when the planetary K index reached 4 and =
Alaska's</FONT>
<BR><FONT SIZE=3D2>College K index reached 6.</FONT>
</P>
<P><FONT SIZE=3D2>Currently on Thursday evening we are affected by a =
high-speed solar</FONT>
<BR><FONT SIZE=3D2>wind stream from a coronal hole causing minor =
geomagnetic storms in</FONT>
<BR><FONT SIZE=3D2>high latitudes. This would result in absorption of HF =
signals over</FONT>
<BR><FONT SIZE=3D2>polar paths. Geomagnetic indices are expected to be =
unsettled to</FONT>
<BR><FONT SIZE=3D2>active over the next few days, and solar flux should =
decline again.</FONT>
<BR><FONT SIZE=3D2>Solar flux is expected to go below 145 by March 10 =
and then reach a</FONT>
<BR><FONT SIZE=3D2>short-term minimum below 110 around March =
22-23.</FONT>
</P>
<P><FONT SIZE=3D2>Since February is over, now we can look at monthly =
average sunspot</FONT>
<BR><FONT SIZE=3D2>and solar flux numbers to spot a trend. Average daily =
sunspot</FONT>
<BR><FONT SIZE=3D2>numbers for September 2002 through February 2003 were =
206.4, 153.9,</FONT>
<BR><FONT SIZE=3D2>159.8, 144.8, 150.0 and 87.9. Average daily solar =
flux for those</FONT>
<BR><FONT SIZE=3D2>same months was 175.8, 167.0, 168.7, 157.2, 144.0 and =
124.5. This is</FONT>
<BR><FONT SIZE=3D2>quite a decline. The average sunspot number for =
February of last</FONT>
<BR><FONT SIZE=3D2>year was nearly 107 points higher at 194.5, and =
average solar flux</FONT>
<BR><FONT SIZE=3D2>was 205, more than 80 points higher than February =
2003.</FONT>
</P>
<P><FONT SIZE=3D2>For more information about propagation and an =
explanation of the</FONT>
<BR><FONT SIZE=3D2>numbers used in this bulletin, see the Propagation =
page on the ARRL</FONT>
<BR><FONT SIZE=3D2>Web site at, <A =
HREF=3D"http://www.arrl.org/tis/info/propagation.html">http://www.arrl.or=
g/tis/info/propagation.html</A> and</FONT>
<BR><FONT SIZE=3D2>especially the article &quot;The Sun, the Earth, the =
Ionosphere,&quot; by Carl</FONT>
<BR><FONT SIZE=3D2>Luetzelschwab, K9LA.</FONT>
</P>
<P><FONT SIZE=3D2>Sunspot numbers for February 27 through March 5 were =
82, 77, 73, 67,</FONT>
<BR><FONT SIZE=3D2>136, 160, and 138, with a mean of 104.7. 10.7 cm flux =
was 117.6,</FONT>
<BR><FONT SIZE=3D2>124.9, 138.1, 147.3, 149.1, 146, and 148.5, with a =
mean of 138.8.</FONT>
<BR><FONT SIZE=3D2>Estimated planetary A indices were 22, 17, 14, 14, =
15, 26, and 16,</FONT>
<BR><FONT SIZE=3D2>with a mean of 17.7.</FONT>
<BR><FONT SIZE=3D2>NNNN</FONT>
<BR><FONT SIZE=3D2>/EX</FONT>
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